The present invention relates generally to implantable electrical leads and more particularly implantable single pass cardiac pacing leads.
It has long been a goal to provide a single cardiac lead which will reliably sense and pace both the atrium and ventricles of a human heart. The simplest approach to providing such lead is simply to add one or more electrodes to the body of a ventricular pacing lead spaced from the distal end of the lead a distance appropriate to locate the added electrodes in the atrium. Such leads are disclosed in U.S. Pat. No. 3,903,897 issued to Woollons and U.S. Pat. No. 3,825,015 issued to Berkovits. While such leads have been proven to sense reliably in the atrium and are currently used in conjunction with VDD pacemakers, their ability to reliably pace the atria is less than might be desired.
Over the years, numerous designs have been proposed and tested which attempted to provide for reliable positioning of the atrial electrodes on a single pass lead adjacent the tissue of the atria in order to allow for reliable cardiac pacing. These approaches have included the provision of active fixation electrodes for use in the atrium as disclosed in U.S. Pat. No. 4,402,329 issued to Williams and U.S. Pat. No. 4,497,326 issued to Curry and the provision of expandable or extendable arms as in U.S. Pat. No. 3,865,118 issued to Bures and U.S. Pat. No. 4,386,615 issued to Sowton.
One of the most common proposals for locating an electrode in the atrium in the context of a single pass lead is the provision of pre-formed loops, coils, or other laterally extending curves formed in the lead body to assist in maintaining an electrode located thereon adjacent the tissue of the atrium. Such leads include U.S. Pat. No. 5,628,778 issued to Kruse et al., U.S. Pat. No. 4,401,126 issued to Reenstierna and U.S. Pat. No. 4,627,439 issued to Harris.
It has also been suggested that an atrial electrode may be stabilized by provision of pre-formed curves, loops or coils proximal to the electrode, intended to be located in the superior vena cava. Such leads are disclosed in U.S. Pat. No. 4,394,866 issued to Hughes and U.S. Pat. No. 5,628,779 issued to Bornzin et al. and in the article "Toward Optimizing a Preshaped Catheter and System Parameters to Achieve Single Lead DDD Pacing", by Brownlee et al., published in Pace, May 1997, Part I, pp. 1354-1358.